This proposal is in response to the NIH and the CIHR call for mechanistic, and/or preclinical research focused on the mechanisms underlying the biomechanical consequences of manual therapies as identified in PAR-06- 312 titled "Biology of Manual Therapy." The broad objective of this project is to understand the biomechanical mechanisms underlying the application of a common form of manual therapy used to treat musculoskeletal conditions by physical therapists, athletic trainers, massage therapists, and others. We plan to develop, test, and apply, innovative, objective musculoskeletal assessment techniques to the shoulder, one of the joints most commonly treated with manual therapy. We will investigate 15 healthy and 15 non-healthy shoulders using real-time magnetic tracking sensors, and subminiature force transducers that are attached to clinicians hands as they perform manual therapy techniques. Electromyography, forces, and joint displacements will be simultaneously recorded. Biomechanical behavior of joint tissue will be characterized by its stiffness, compliance, and viscous responses. We will record expert clinicians'ability to reproduce specific techniques. The long-term goals are to expand the assessment method to other joints, determine the effectiveness of manual mobilization for restoring mobility in patients with musculoskeletal joint dysfunction, and to establish biomechanically based parameters to distinguish, categorize and diagnose healthy and non-healthy tissue. A corollary goal is to provide clinicians with an objective, cost effective tool to document manual assessment and treatment of joint dysfunction. Specific aims: 1.Characterize the biomechanical behavior and the associated muscular reflex responses resulting from manual mobilization techniques applied to the shoulder using both healthy and impaired shoulders. 2. Distinguish healthy vs. impaired tissue responses based on the shoulder joint's biomechanical behavior during manual application of specific mobilization techniques 3. Clarify key theoretical constructs used in formulation of mobilization approaches: A. The "close-pack" and "loose-pack" position of joints, and, B. The clinical response known as "End-Feel." 4. Measure and objectively define the differences between Maitland's clinical grades (I-IV) of mobilization as performed by experienced clinicians and 5. Evaluate our portable laptop based measurement and assessment system in local area clinics using field focus group analysis. Our study will result in a user-friendly, user- configurable, portable motion and force measurement system that can be used for most major joints as a treatment assessment, examination, and teaching tool. Focusing our initial study on the shoulder joint provides the best model for multidirectional treatment technique evaluation, and allows us to identify distinct tissue pathologies over a broad spectrum, from shoulder instability to frozen shoulder, so that a continuum of tissue responses can be studied. PUBLIC HEALTH RELEVANCE: Manual therapies constitute the overwhelming percentage of conservative treatment approaches for musculoskeletal conditions. Research directed to the understanding of how these approaches affect the body is fundamental to an evidence-based medical practice system. Our proposal is highly relevant to public health since it provides both mechanistic understanding, and practical tools and methods for scientifically evaluating a common form of manual therapy used by massage therapists, athletic trainers, chiropractors, physical therapists and other "body work" therapists.